Summary: Unlike conventional biochemical and molecular approaches, DNA microarray technology represents new era in biological science that brings along a new set of paradigms. This technology can enable discovery of unknown patterns and biological processes without a piori assumptions. One can assess status of thousands of genes at once which was not possible by conventional means. It is believed that this technology will impact on the development of new sets of biotechnology products. After establishing a CBER/NCI Interagency Agreement (IAG), a microarray laboratory was developed. This laboratory has been renovated, equipments purchased and now operational. Research programs focus on 1) development of arrays for the identification of potential presence of adventitious agents in cell substrates used to manufacture biological products or presence of these agents in the products themselves 2) developent of oligonucleotide chips containing genes from human pathogens to be used for detecting pathoges in affected population. These chips will help identify specific gene expression changes in target tissues by specific pathogens for data base development and future identification of pathogens in infected population. Expression of different genes will help identify protein targets for development of therapeutic agents in countering bioterrorism 3)developemnt of tests for identity of therapeutic tumor vaccines by expression profiling. 4) Plans are being made to use this technology in the characterization of identity, differentiation state and quality of human embryonic stem cell products. Additional studies will be undertaken once the program is completely operational.